1. Field
The present disclosure relates generally to methods for enhancing chemical reactions, and more specifically to enhancement of chemical reactions through the use of nanomaterials.
2. Description of Related Art
X-ray absorption by materials has been broadly used in imaging, lithography, and treatment since the discovery of X-rays. Nanomaterials, which were widely used as catalysts decades ago, are being intensely explored in many fields, especially biology. The use of previously considered inert nanomaterials such as gold nanoparticles to increase the absorption of X-rays began a few years ago, and many chemical and biological responses have been used to quantify the enhancement.1,2 Because gold nanoparticles can be catalytically active under suitable conditions,3-9 it is likely that these nanomaterials may do more than simply enhance the absorption of X-rays in a highly reactive environment such as those created by X-ray radiation. However, all of the observed enhancements to date have been attributed to physical properties of the nanomaterials, i.e., high atomic numbers, leading to increased X-ray absorption and subsequent increased generation of reactive oxygen species (ROS), even though the observed enhancements could be much higher than the values predicted on the basis of the physical enhancement at low loadings (<0.1 wt %) of nanoparticles1,10 or much lower at high loadings (˜1 wt %) of nanoparticles.11 These disagreements indicate that physical enhancement alone, even taking into account reabsorption of emitted secondary photons and electrons,12 which is negligible, cannot explain the observed enhancement.